The marketing, distribution and sale of consumer products and other similar products often requires considerable attention to the design of the containers used to package such products. It generally is desirable to provide such containers with a feature that permits the purchaser to open the container with a minimal amount of physical effort. For many containers, such "easy open" features are intended to be operable by pressing a thumb or finger against a portion of the container designated as the opening location, such as a hinged tab that is depressed into the interior of the container. It often is desirable to provide such containers with opening features that also form a dispensing aperture, particularly in containers used for dry and pourable products of various sizes.
Many such opening features are found in existing container designs for paperboard cartons. Such containers typically are made from a precut, unitary blank having various score and die cut lines that permit the automated folding, forming, filling and sealing of the containers. The opening features in such containers often include an opening tab formed by a series of partial perforations or cut lines in the surface of a container wall in the shape of a "V", a "U", an oval, a rectangle or similar shapes. The container is opened by depressing the tab into the interior of the container so that the container wall ruptures or tears at the tab borders along such partial perforations to form an aperture for dispensing the contents of the container.
Such opening tabs may be located at various parts of the containers, and typically are found at the upper portions of a side panel or on the top panel of the container. In paperboard and similar containers, such opening tabs frequently remain connected to the container wall along a hinged side so that the tab is not intermixed with the contents of the container. Containers using such tabs may include complicated pour spouts, various reclosing features and multi-part dispensing controls that operate or become accessible once the tab is depressed and the dispensing aperture is formed.
In other containers, the opening tab and the dispensing aperture act as a finger grip that allow the user to create a larger opening in the container. In such designs, the opening tab is depressed into the interior of the container and the user further inserts a finger or thumb into the resulting aperture. The user continues to pull on the tab, typically towards the top of the container, to peel back the top panel of the container and to create a much larger dispensing aperture. In some designs, the container top panel may be removed entirely, and in others the top panel is designed to fold back on itself or on a hinged portion of the top panel.
The use of an opening tab to provide an aperture and grip to further open the container may be employed in containers for bulky, pourable products such as pastas, cereals and similar food stuffs. This feature also is used for dry foods and other products made of fine particles that are difficult to pour or that have a tendency to cake or clump together, such as flours, bakery mixes, dry soaps, etc. Such opening systems, in addition, may be used for dry products that are used in bulk quantities or are easily damaged and therefore require a large dispensing aperture.
The design of easy open features requires consideration of a number of objectives and performance requirements. For many containers, including paperboard containers, an easy open design must be integrated into the overall container structure with the minimum of complicated or added components. For example, the easy open features in paperboard containers frequently must be integral to a unitary blank used to form the container. It is desirable to avoid the need for additional tabs, flaps, folds, glues, inserts, reinforcements or the like to form the easy open feature to reduce the cost of the container and the steps needed to form the container.
In food containers, easy opening features further require due care to maintain a barrier between the food within the container and the outside environment. Such barriers frequently are necessary to preserve the contents of the container in a safe, sanitary condition and to prevent spoilage of the contents. The barriers must prevent infestation of container contents by insects or microorganisms from the outside environment. In some applications, the barriers must prevent the loss or gain of moisture by the container contents and prevent oxidation or other atmospheric reactions with container contents. It also frequently is desirable to provide such barriers without the use of additional inner liners or overwraps. The same concerns typically apply to non-food products that may be adversely affected by exposure to the environmental conditions outside of the container.
The easy open features in such containers must not compromise the structural integrity and strength of the container. Paperboard containers often are subjected to a variety of impact loads and stress during shipping and handling of the containers in commercial channels of commerce (i.e., trucking, warehousing and shelf stocking) as well as the use or misuse of the container by the end consumers. These stresses and loads include columnar and crush loading during the packing of individual containers in shipping cases and in palletizing the cases for storage at warehouse facilities, as well as vibrational stress during shipment and movement of pallets of the containers. Additional loads may be imposed in warehouse storage when multiple pallets of product are stacked and restacked on top of one another to efficiently utilize warehouse space. In addition, during shipping and storage, the cartons are frequently subject to crush loads, tensile loads and potential penetration by random objects.
Once the containers reach a retailer, they may be subjected to additional stresses and loads during the shelving and display of the product due to, for example, dropped containers, insufficient storage space and misuse of the containers. The end consumers purchasing such containers may subject the containers to additional unexpected stresses. For example, individual containers may be exposed to drops from a variety of heights, crushing weights, shaking, tossing and piercing events that may result in breaches of the container's structural integrity.
Such loss of structural integrity can be evident from obvious deformation of the container, leaks, tears, punctures, and product spoilage. More subtle defects in the container due to shipping and handling stresses include delamination of a container surface and separation of the seals in the container, including those in an easy open feature of the container. These types of failures may be reported directly to the product manufacturer or packager, or they may go unnoticed in unsalable containers returned to a manufacturer without explanation. Accordingly, it is desirable for easy opening container designs to provide features capable of withstanding all of the above stresses and loads without causing container failures or defects, particularly those leading to spoilage or permitting infestation of the container contents. This capability is particularly desirable in paperboard or similar containers which do not employ an inner liner or overwrap such that product leakage and/or contamination may occur readily as a result of loss of integrity of a single wall or opening tab.
One attempt to provide a suitable easy opening feature for paperboard containers was to partially perforate the side panel of a carton from the exterior to a depth less than the thickness of the paperboard. The partial perforations were arranged in one or more rows in "V", "U", or rectangle shapes. The perforations left sufficient paperboard in the perforated area to prevent infestation and to preserve the side panel strength.
To open such containers, the user pressed on the tab area formed by the perforations and pushed the tab into the container. However, these tabs frequently required considerable opening force because the perforations did not fully penetrate the panel and were not of sufficient size to permit easy opening of the container due to concerns about compromising the strength of the container and its resistance to stresses and loads during shipping and handling procedures. The force required to open prior tabs in many instances caused the carton panels to deform, bend or even collapse, and could render the tab itself inoperable.
These types of problems lead to consumer frustration and complaints, as well as the possible loss of sales and increased costs for returned goods. In most instances, the number and depth of the prior perforations could not be practically increased to render the cartons easier to open without weakening the tab area to the point where inadvertent opening, the loss of structural integrity, possible infestation and spoilage became a serious concern.
One alternative approach for an easy open feature used spaced, opposing, "reverse" cuts in the side panel of a paperboard container to form an opening tab. For example, in Zimmerman, U.S. Pat. No. 3,521,809, paperboard cartons are provided with a tab formed from correlated edge cuts spaced from marginal cuts, each of which extended partially through the paperboard from opposite sides of the board stock. The correlated cuts extended from the container side panel into the top panel of the container. The correlated cuts defined a plane of cleavage between the inner extremities of the two cuts about which the paperboard could be fractured by manual pressure.
This design, however, lacked protections from unintentional opening or leaks in the tab due to packing, shipping, storage and use stresses and loads. The advantages of any reduction in opening pressures required to operate the tab in such designs could be offset in many instances by the possibility of the opening tab's premature failure and breach of the container wall. Such designs also encouraged the partial failure of the tab through paperboard delamination and similar failures that disfigured the container and discouraged the sale of the contents of the container.
In Collura et al., U.S. Pat. No. 3,735,914, a removable portion of a container side panel was formed by a pair of generally parallel cut lines which extended only partially through the carton side wall from the outside and inside faces of the paperboard. These lines formed a line of weakness in the paperboard, and additional paperboard flaps ("Van Buren ears") were folded over the panel to reinforce the upper part of the removable portion. The additional reinforcement addressed one problem with earlier "reverse cut" opening features, but increased the cost of the packaging, and complicated forming and filling the container.
The invention provides an opening system that provides the easy opening features desired by manufacturers, packagers and consumers without the disadvantages of the prior opening systems. The invention is further described below.